Expansion anchor

ABSTRACT

An expansion anchor includes an anchor bolt, a nut, a spring washer, first and second outer metal plates, and first to fifth inner metal plates. Each of the first and second outer plates is subjected to the dovetail-correspondence elevation-angle bending-processing. The width of the first to fifth inner metal plates is set larger in the order of the fifth inner metal plate to the first inner metal plate, and the upper portions or the whole surfaces of the four side surfaces of the first to fifth inner metal plates are subjected to the chamfering-processing so that they become the continuation surfaces with the same inclination angle as the side-wall of the dovetail when the first to fifth inner metal plates are piled up in the same direction.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an expansion anchor, especially to anexpansion anchor suitable to be used in combination with a dovetail.

2. Description of a Related Art

Conventionally, the drilling method in the “post-installed anchor” workis mainly carried out using a hammer drill. In this drilling method,since the intentional base-material organization destruction by the oneperpendicular both-way blow movement to the object surface and thepowdering by the 2-level rotational movement boring are the drilling(hole-forming) element, there are following problems.

(1) Since the hair crack occurrence caused by vibration is inescapable,the anchor power (grip power) is declined by the aged deterioration, sothat the supported-material omission accidents occur frequently.(2) Although the “edge-width dimension” security is indispensable inorder to collateralize the safety margin to the intentionalbase-material organization destruction portion by the one perpendicularboth-way blow movement, the construction which does not satisfy the“edge-width dimension” prescribed by JIS about the vending-machine fallprevention anchoring is actually rampant, so that the dangerous fixedsituation where the proof stress is hardly demonstrated at the time ofthe earthquake calamity is becoming commonplace.

On the other hand, although the drilling by the core-drill is alsoperformed, it is restrictively used. Because it does not give the shockmechanical vibration to the base material, but the equipments and themachines become large-scale, and it is the cutting by the waterinjection type.

There are the following patent document 1 and non-patent documents 1-6as the documents which describe the problems about the “post-installedanchor.”

Patent Document 1: JP-A-2000-192926. Non-Patent Document 1: M. Hirosawaand Y. Shimizu, “Commentary on the Goods, Structural Design and SideExecution of Post Installed Anchors”, Concrete Journal, Vol. 31, No. 4,pp. 13-30, April, 1993.

Non-Patent Document 2: Prof. Rolf Eligehausen in Stuttgart TechnicalUniversity, Lecture Material “Introduction of Pouring-type Bonded Anchorand Reinforcing-Steel Establishing Method in Europe Adopted ofPouring-type Bonded Anchor”, Hilti and Japanese Hilti Sponsorship, HiltiFastening Academy 2004.

Non-Patent Document 3: Choshiro Ogawa (Saitama Stone BusinessAssociation Youth Part Standing Director), “Miyagi Prefecture NorthernPart Earthquake Damage Investigation Report”, Chapter 2. Non-PatentDocument 4: Meteorological Agency, “Seismic Intensity 5+, ManyGravestones Fall”, Meteorological Agency Intensity Scale DescriptionTable. Non-Patent Document 5: APAN DRIVE-IT CO., LTD., MetalSafety-Device-Against-Wind System Product Specification DimensionsTable. Non-Patent Document 6: Diamond Product Company, PhotographsInserted in “Flatting Out of Construction.” Non-Patent Document 7: T.Okada et. al., “Design and Construction of Post-Installed Anchor”, JapanConstruction Anchor Association Recommendation Books.

In the non-patent document 1, the following matters are described.

(1) The rotation/shock-type rotary hammer drills having good drillingperformance are imported from U.S.A. and Europe in the second half ofthe Showa 30 s, and the various types of anchors come to be used widely.(2) The 1990 fiscal-year production volume of the metal-system anchorand the adhesion-system anchor (bonded anchor) is 420 million, and shows10-12% of elongation every year.(3) The base metals at the use parts are also various, such as concrete,a section, brick, etc. There is also usage which can be investigatedlike the fixing (anchoring) of the vending machine specified by JIS, butin the other case, the kind of the anchor to be used also has the factthat the selection lacked in the dynamics consideration is performed.(4) Moreover, there are also many questions such as a constructionmanagement, an amendment of construction mistake, an inspection method,etc., and the cures against them pose the future big problems.(5) In Japan, there is no JIS standard about the “post-installedanchor.”(6) Also about the construction method, there are no public standardconstruction specifications about the “post-installed anchor” in Japan.(7) There are the oscillating twist drill, the hammer drill, the rockdrill, and the diamond core-drill as the drilling machine.(8) In the metal-system anchor, the construction standard is definedaccording to the kind and path of the bolt to be used, but when it isincongruent, the anchor efficiency declines remarkably.(9) In the adhesion-system anchor, the remarkable efficiency degradationoccurs when the removal of the powders is neglected at the cleaning ofthe holes.

The following analysis results are shown in the non-patent document 2.

(1) The adhesion stress (bond stress) distribution is stabilized in theembedding depth of 60 mm or more.(2) The adhesion stress is decreased to 33% or less of the rated valueswhen the adhesion stress determination factors (the drilling diameter,the hole-inner cleaning, and the drilling method) are neglected,especially when the hole-inner cleaning is neglected. The adhesionstress is decreased in the abbreviation half of the rated value by onlyone blower cleaning.(3) When the edge-width dimension is 50 mm or less, it results in thebreak-down by the slight displacement and loading.(4) The poor adhesion caused by the air remainder after the adhesivespouring occurs.(5) Moreover, it should be constructed by the skilled manual labor (theconstruction grade system exists in Germany.).(6) The conclusions of the adhesion anchor:(a) An adhesives-pouring-type anchor is a reliable “post-installedanchor” like the conventional capsule type. However, the anchorperformance depends on the hole-inner cleaning and the drilling method.(b) About the action efficiency of the “post-installed anchor” underearthquake, the further research and experiment are required.(c) In the concrete in which the crack has occurred, the break-downtakes place by the interface between the resin and the concrete, and thebreak-down proof strength declines about 50% as compared with concretewithout any cracks. In the concrete in which the crack has occurred, thespecial expansion anchor is effective. This is the anchor having thestructure of maintaining the adhesion stress by the gauge pressure ofthe extended part of the bolt.

In the lecture entitled “Role and Importance of Post-installed Anchor inBuilding Equipment Earthquake-Proof Construction,” by Prof. ToshiakiKiuchi in Kokushikan University, Technology Faculty, Architecture DesignEngineering Department, in Hilti Fastening Academy 2004 sponsored byHilti and Japanese Hilti, the following matters are stated.

(1) The various kinds of the earthquake-proof efficiency examinationsincluding the anchor bolt was performed in “Tokyo Shirakami-AreaPlanning” about one year before the earthquake occurred off MiyagiPrefecture in 1978.(2) The earthquake occurred off Miyagi Prefecture in 1978 during thedeliberation on “Guideline of Private-Power-Generation Anti-earthquakeDesign” (only the “post-installed anchor technical standard” in Japan).(3) About the post-installed anchor metal expansion type for buildingequipment, the permission drawing-out standard value is accepted after1982 and afterwards. However, at the construction job site, in practice,the usage method is left in many cases to the builders who carry out thepiping etc. including the site foremen, the construction supervisorengineer, the design person in charge, and the person in chargespecializing in the construction company. However, since the anchorfall-out accident occurred frequently in various places, the accidentpreventive measures (for example, the checks of the kind, constructionmethod, permission drawing intensity and strength have been taken in1990 and afterwards (It will be the occurrence of Kobe Earthquake in1995 in the midst of the measures being taken.).(4) The post-installed anchor (HASS) standard is under deliberation in2005 (Although about 30 years have passed since the first examination in1977, it is the present condition that it cannot be determined.).(5) The drawing power (tenacity) of the constructed “post-installedanchor” must fulfill the value of permission drawing power 100%. Thatis, there must not be any construction mistake by any means. The badinfluence of one occurrence of the accident is carried out to thefunctionality of the whole building. There is fear of falling into thecondition which cannot use the whole building depending on the case.Moreover, also especially in a big earthquake (magnitude 7 on theJapanese scale), the “post-installed anchor” must have the proofstrength in all break-downs.(6) Immediate realization of the world common standard for construction“post-installed anchor” is desired. In this case, it is conditions tokeep the unified technical standard 100%.

In the above-mentioned patent document 1, the following matters aredescribed as the weak points of the expansion-bottom anchor indicatedabout the anchor bolt.

(1) A crack produces to the concrete according to the power whencarrying out the expansion when the anchor is inserted. Moreover, thecontact surface is worn out with progress of time owing to themechanical vibration. As a result, the anchor bolt loosens and jolts.(2) The weak points of the adhesion-system anchor described in Paragraph0004.(3) The adhesive overflows from the bolt hole.(4) Since time will be taken before solidifying, the anchor bolt shiftsand inclines from the central axis of the bolt hole. Actually, themetal-system anchor and the adhesion-system anchor have the unstablegrip power over the base material.

In the above-mentioned non-patent document 3, it is indicated that theanchor bolt such as a deformed bar is weak to the epicentral earthquake.

In the above-mentioned non-patent document 4, it is described “there isdescription of the fact that many gravestones collapsed, in NiigataChuetsu Big Earthquake which occurred in October, 2004. Moreover, alsoin the gravestone in which it was equipped with the anchor bolt, theanchor bolt crawled, reached and fell out and collapsed. The cause wasthe vibration of the shortage of the mortar enclosure, etc. and theearthquake.”

If the size standard table of the metal extension anchor is quoted andit compares based on the frequently-used diameter of a screw [M10],

1. Internal corn placing type

Diameter of boring drill: 12.0 mm/12.5 mm, Boring depth: 40 mm>

2. Shaft-sleeve placing type

Diameter of boring drill: 14.0 mm/14.5 mm, Boring depth: 45 mm>

3. Wedge type

Diameter of Boring drill: 10.0 mm/10.5 mm, Boring depth: 60 mm>

As mentioned above, the size which guarantees the anchor intensity isspecified. When the diameter of the boring twist drill is mistaken,although it is somewhat loose, it loads as it is. Or, since it iscompletely loose, it re-bores. As mentioned above, it is unstable andinefficient as the work which is done by a person who easily makes amisapprehension and a mistake (refer to the above-mentioned non-patentdocument 5).

As shown in the photograph published by the above-mentioned non-patentdocument 6, when the drill is held by hands, it is difficult in thestock drill operation to hold it so that the rotation core may not blurand to secure the perpendicular to the boring surface.

The defect of the boring operation using the hammer drill and the coredrill, and the defect of the metal-system anchor and the adhesion-systemanchor are summarized as follows:

(1) The shock boring method crushes the solid composition of the basematerial.(2) When carrying out the on-site hammer drill operation, it isdifficult to bore right-angled to the base material surface because ofthe narrow place and the influence by the hammer drill's own weight. Inorder to actually keep the worker's eye point on the hammer drill coredrill axis-of-rotation extension, and in order to stop the boundthrowing of the drill which certainly occurs at the time of theabove-mentioned equipments operation, it stands and is space (1 m×1m×less than 2 m in width) required for operation. In the job site, theplace in which the drilling is possible will narrow naturally. “Slantingboring” occurs by work of the labored posture. The job called “standcuring” as a method of correcting this slanting boring becomesinescapable. It is the method of bending the external-thread boltforcibly and making it perpendicular after the external-thread insertionafter anchor wearing. Also in this case, the perpendicular standardsetup is difficult. Moreover, the high-precision amendment is difficultbecause of the narrow working area. The perpendicular boring isdifficult and is the fatal flaw which loses the anchor drawing intensitywith blow boring.(3) The edge-width-dimension reservation is difficult. When theedge-width dimension is 50 mm or less, it has almost no proof strength.(4) When the reinforcing steel is encountered, you have to re-bore thepart which made the mistake in keeping the fixed distance. Therefore,there is fear of changing the design of the related materials.(5) In the government office order construction, the photograph of thedepth of the bored hole must be taken, and the survey must be undergone.(6) The inner cleaning is complicated, and the anchor efficiency ishalved only by blower cleaning.(7) Air will be enclosed of the pouring-type adhesion-system anchor. Asa result, the adhesion stress declines.(8) The anchor construction qualified person (journeyman) in Germany andthose who pass the “post-installed anchor” construction technical expertexamination in Japan are allowed the construction of the anchor.(9) There are no anchor common protocol, standard construction technicalspecification, etc.(10) The mistake and the misapprehension occur inevitably because it iscomplicated since there are many kinds of anchors and the diameter ofthe matching boring drill changes. Moreover, you have to re-boresomewhere else in that case. Therefore, it is easy to become the hotbedof the negligent construction work. After the omission accidentsactually happened in succession, the construction persons concerned allover the country took the counterplan with all their might.Nevertheless, the accident will occur frequently. The reason depends thehundred percent inspection on the impossible thing.(11) Moreover, even if it gives the high-precision anchor charge, theoccurrence of the crack is inescapable as it passes through time fromthe characteristic of concrete. In the base material in which the crackoccurs, 100% of anchor-efficiency exertion is difficult (It decreases to50%.).(12) Precise horizontal/vertical fixation is required of the apparatuslocked up. When it must install by the slanting hole unavoidably,because the bolt axis is slanting, the screwing work with the main partof apparatus and matrix material concrete is difficult.

The incongruent anchor actually which cannot be grasped and follow-upsurvey are rampant.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an expansion anchorwhich can realize the practical-use strength and the proof strengthdemanded in the shallow dig depth.

An expansion anchor of the present invention is an expansion anchor usedin combination with a dovetail, a mouth width of the dovetail beingnarrower than a bottom width of the dovetail, and includes: an anchorbolt; two or more inner metal plates inserted into the dovetail; and twoouter plates inserted between two side-walls of the dovetail and theinner metal plates, wherein each of the two outer plates has “L”character-like cross-sectional shape which consists of a top plateportion and a side plate portion.

An expansion anchor of the present invention is an expansion anchor (10)having an external thread at one center place of a “−” character-likeshaped dovetail (31, 31′), a mouth width of the dovetail being narrowerthan a bottom width of the dovetail, and includes: an anchor bolt (11);a nut (12); first and second outer plates (15 ₁, 15 ₂); and two or moreinner metal plates (16 ₁-16 ₅), wherein each of the first and secondouter plates has “L” character-like cross-sectional shape which consistsof a top plate portion and a side plate portion; and width of one innermetal plate of the two inner metal plates is set larger than width ofanother inner metal plate.

Here, length of the another inner metal plate of the two inner metalplates may be set larger than the width of the one inner metal plate, sothat side surfaces of the two inner metal plates become surfaces havingthe same inclination angle as a side-wall of the dovetail when the oneinner metal plate is turned 90 degrees to be piled on top of the anotherinner metal plate of the two inner metal plates.

Width of at least one inner metal plate of the two inner metal platesmay be set larger than the mouth width of the dovetail; and apenetration-hole, a bore of which is larger than a diameter of theanchor bolt, may be provided in a center portion of the at least oneinner metal plate of the two inner metal plates.

An expansion anchor of the present invention is an expansion anchor (50)having internal threads at two end portions of a “−” character-likeshaped dovetail (31, 31′), a mouth width of the dovetail being narrowerthan a bottom width of the dovetail, and includes: first and secondanchor bolts (51 ₁, 51 ₂); first and second outer plates (55 ₁, 55 ₂);and upper inner metal plate (56 ₁) and lower inner metal plate (56 ₂),wherein each of the first and second outer plates has “L” character-likecross-sectional shape which consists of a top plate portion and a sideplate portion; and first and second upper internal threads (56 a ₁₁, 56a ₁₂) and first and second lower internal threads (56 a ₂₁, 56 a ₂₂), bywhich tap-processing is carried out to screw with the first and secondanchor bolts, are formed in the upper inner metal plate and the lowerinner metal plate.

Here, width of the upper and lower inner metal plates may be set smallerthan the mouth width of the dovetail; a sectional shape of the lowerinner metal plate seen from a perpendicular direction to lengthdirection of the lower inner metal plate when cutting in the lengthdirection of the lower inner metal plate is made into areverse-trapezoid shape; and each width of the side plate portions ofthe first and second outer plates is set smaller toward a bottom portionfrom a central portion when seeing along height direction of the sideplate portion.

An expansion anchor of the present invention is an expansion anchor (60)having internal threads at four end portions of a “+” character-likeshaped dovetail (32, 32′), a mouth width of the dovetail being narrowerthan a bottom width of the dovetail, and includes: first to fourthanchor bolts (61 ₁-61 ₄); first to eighth outer plates (65 ₁-65 ₈); andupper innermetal plate (66 ₁) and lower innermetal plate (66 ₂), whereineach of the first to eighth outer plates has “L” character-likecross-sectional shape which consists of a top plate portion and a sideplate portion; the upper inner metal plate and the lower inner metalplate have shape similar to the shape of the dovetail when seen at aplane; first to fourth upper internal threads (66 a ₁₁-66 a ₁₄), bywhich tap-processing is carried out to screw with the first to fourthanchor bolts, are formed in first to fourth upper projection portions ofthe upper inner metal plate; and

first to fourth lower internal threads (66 a ₂₁-66 a ₂₄), by which thetap-processing is carried out to screw with the first to fourth anchorbolts, are formed in first to fourth lower projection portions of thelower inner metal plate.

Here, each width of the first to fourth upper projection portions of theupper inner metal plate and the first to fourth lower projectionportions of the lower inner metal plate may be set smaller than themouth width of the dovetail; tip portions of the first to fourth lowerprojection portions of the lower inner metal plate are cut by an acuteangle toward a bottom portion of the lower inner metal plate; and eachwidth of the side plate portions of the first to eighth outer plates isset smaller toward a bottom portion from a central portion when seeingalong height direction of the side plate portion.

That is, the expansion anchor (dovetail anchor) of the present inventionis the metal expansion anchor, and is locked up in the dovetail, whichis formed in the base material by the rotation of the blade and chain(for example, the diamond saw and the diamond chain saw) in order toovercome the defects of the conventional circular-hole boring expansionanchor.

The shape of the dovetail dug to the base material and the shape of thematching anchor are “−” character-like and “+” character-like on thelooking-down plan view. Moreover, the screwing portions are prepared inmany parts including one center place or the end portions. Furthermore,either the internal thread or the external thread can be used accordingto the demanded proof strength and conditions.

The expansion anchor of the present invention tends to acquire the pullproof strength and shearing proof strength of the anchor using it incombination with the dovetail (the slot the mouth width of which is setsmaller than the bottom width). Therefore, it is impossible to beinserted into the dovetail with one parts and one-article parts becauseit is the component corresponding to the width of the dovetail, so thatthe parts are molded into plurality and the parts are separatelyinserted into the dovetail. After the insertion of the parts, each ofthe parts is made one, connected and expanded utilizing the boltscrewing function to demonstrate the stress and the power-proof whichare demanded to the anchor.

Conventionally, the group effect (namely, the dramatic reduction of theanchor proof strength by the lap of the project area) in the conebreak-down is inescapable when four anchors are locked up at thehigh-density places and the narrow places. However, the expansion anchorof the present invention has the technical effect to realize thepractical-use strength and the proof strength demanded in the shallowdig depth, because the cause of the proof-strength attenuation combinedwith the base-material break-down according to the mechanical vibrationat the time of forming the anchor hole can be avoided 100%.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing the composition of an expansion anchor 10according to the first embodiment of the present invention.

FIGS. 2A and 2B are drawings explaining the forming method of a “−”character-like dovetail, FIG. 2A is a diagram showing a diamond wheelsaw 21 used for forming the dovetail, and FIG. 2B is a drawing showing adiamond chain saw 25.

FIGS. 3A-3D are drawings explaining the forming method of a“−”character-like dovetail, and show the steps of forming a dovetail 31 ina base material 30 using the diamond wheel saw 21 shown in FIG. 2A.

FIGS. 4A and 4B are drawings showing the shape of the “−” character-likedovetails 31, 31′, FIG. 4A is a drawing showing the shape of thedovetail 31 formed using the diamond wheel saw 21 shown in FIG. 2A, andFIG. 4B is a drawing showing the shape of the dovetail 31′ formed usingthe diamond chain saw 25 shown in FIG. 2B.

FIGS. 5A-5D are drawings showing the state of the locked-up expansionanchor 10 shown in FIG. 1, FIG. 5A is a looking-down plan view, FIG. 5Bis a looking-up plan view, FIG. 5C is a side view, and FIG. 5D is anelevation view.

FIG. 6 is a drawing showing the composition of an expansion anchor 50according to the second embodiment of the present invention.

FIGS. 7A-7D are drawings showing the state of the locked-up expansionanchor 50 shown in FIG. 6, FIG. 7A is a looking-down plan view, FIG. 7Bis a looking-up plan view, FIG. 7C is a side view, and FIG. 7D is anelevation view.

FIG. 8 is a drawing showing the composition of an expansion anchor 60according to the third embodiment of the present invention.

FIGS. 9A-9D are drawings explaining the forming method of a “+”character-like dovetail, and show the steps of forming a dovetail 32 ina base material 30 using the diamond wheel saw 21 shown in FIG. 2A.

FIGS. 10A and 10B are drawings showing the shape of the “+”character-like dovetails 32, 32′, FIG. 10A is a drawing showing theshape of the dovetail 32 formed using the diamond wheel saw 21 shown inFIG. 2A, and FIG. 10B is a drawing showing the shape of the dovetail 32′formed using the diamond chain saw 25 shown in FIG. 2B.

FIGS. 11A-11D are drawings showing the state of the locked-up expansionanchor 60 shown in FIG. 8, FIG. 11A is a looking-down plan view, FIG.11B is a looking-up plan view, FIG. 11C is a side view, and FIG. 11D isan elevation view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of an expansion anchor according to the presentinvention will be described with reference to the drawings.

An expansion anchor 10 according to the first embodiment of the presentinvention is used as an expansion anchor which has an external thread atone center place of a “−” character-like shaped dovetail 31 (refer toFIGS. 4A and 4B). As shown in FIG. 1, the expansion anchor 10 includesan anchor bolt 11 (a hexagonal-head bolt) made from steel, a nut 12 madefrom steel, a spring washer 13 made from steel, an anchorage metal plate14 made from steel, the first and second outer plates 15 ₁, 15 ₂ madefrom steel or a plastic, and the first to fifth inner metal plates 16₁-16 ₅ (4.5 mm in thickness) made from steel.

Here, each of the first and second outer plates 15 ₁, 15 ₂ has “L”character-like cross-sectional shape which consists of a top plateportion and a side plate portion formed in one. The side plate portionsof the first and second outer plates 15 ₁, 15 ₂ are bent to the topplate portions at the inclination angle so that the side plate portionsbecome parallel to the side-walls of the dovetail 31 when inserting thefirst and second outer plates 15 ₁, 15 ₂ into the dovetail 31 so thatthe end surfaces of the top plate portions face each other. That is, thefirst and second outer plates 15 ₁, 15 ₂ are subjected to thedovetail-correspondence elevation-angle bending-processing. Although itis more desirable that the first and second outer plates 15 ₁, 15 ₂ aresubjected to the dovetail-correspondence elevation-anglebending-processing, they may be ones which are manufactured by cuttingthe ready-made article angle (for example, a right-angled bendingmaterial like an iron-material angle cutting plane).

Moreover, the first and second outer plates 15 ₁, 15 ₂ have the functionfor transmitting the short-term load and the long-term load (tensileforce and shearing force), which are generated after providing theanchor, to the side-walls of the dovetail 31 uniformly and on theaverage. The first and second outer plates 15 ₁, 15 ₂ may be made frommetal such as steel in the usual application, but they may be made fromplastic in the special-purpose application such as electric-insulationgoods.

In the center portion of the anchorage metal plate 14, apenetration-hole, the bore of which is the almost same size as thediameter of the anchor bolt 11, is provided.

Moreover, in the center portions of the first to fifth inner metalplates 16 ₁-16 ₅, penetration-holes, the bore of which is larger thanthe diameter of the anchor bolt 11 (that is, with a margin), isprovided.

The width (the length of the width direction of the dovetail 31) of thefirst to fifth inner metal plates 16 ₁-16 ₅ is set so that “the width 1Wof the first inner metal plate 16 ₁”<“the width 2W of the second innermetal plate 16 ₂”<“the width 3W of the third inner metal plate 16₃”<“the width 4W of the fourth inner metal plate 16 ₄”<“the width 5W ofthe fifth inner metal plate 16 ₅”. The length (the length of thelongitudinal direction of the dovetail 31) of the first to fifth innermetal plates 16 ₁-16 ₅ is set so that “the length 1L of the first innermetal plate 16 ₁”<“the length 2L of the second inner metal plate 16₂”<“the length 3L of the third inner metal plate 16 ₃”<“the length 4L ofthe fourth inner metal plate 16 ₄”<“the length 5L of the fifth innermetal plate 16 ₅.”

Here, the width 5W of the fifth inner metal plate 16 ₅ is set largerthan the mouth width W1 of the dovetail 31.

However, if the sum of the thickness of the side portion of the firstouter plate 15 ₁, the width 5W of the fifth inner metal plate 16 ₅ andthe thickness of the side portion of the second outer plate 15 ₂ islarger that the mouth width W1 of the dovetail 31, the width 5W of thefifth inner metal plate 16 ₅ may be smaller than the mouth width W1 ofthe dovetail 31.

Moreover, the upper portions (or the whole surfaces) of the four sidesurfaces of the first to fifth inner metal plates 16 ₁-16 ₅ aresubjected to the chamfering-processing so that they become thecontinuation surfaces with the same inclination angle as the side-wallof the dovetail 31 when the first to fifth inner metal plates 16 ₁-16 ₅are piled up in the same direction in order of the fifth to first innermetal plate 16 ₅-16 ₁. However, although it is more desirable that thefirst to fifth innermetal plates 16 ₁-16 ₅ are subjected to thechamfering-processing, they may be ones which are manufactured by beingextracted by the press-working machine and are not subjected to thechamfering-processing.

Moreover, the length 1L of the first inner metal plate 16 ₁ is setlarger than the width 5W of the fifth inner metal plate 16 ₅ (namely,5W<1L), the chamfering-processed upper surfaces of the side surfaces ofthe first to fifth inner metal plates 16 ₁-16 ₅ become the continuationsurfaces having the same inclination angle as the side-wall of thedovetail 31 when the fifth inner metal plate 16 ₅ is turned 90 degreesto be piled on top of the first inner metal plate 16 ₁.

Thereby, even when the tolerance between the width of the dovetail 31formed in a base material 30 and the original marking width occurs, theoptimal expansion width can be gained. For example, when a set of theinner metal plates in which the first inner metal plate 16 ₁ is used asthe lowest stage and the fifth to second inner metal plates 16 ₂-16 ₅are turned 90 degrees to the first inner metal plate 16 ₁ to be piled ontop of the first inner metal plate 16 ₁ in this order (1L>5W>4W>3W>2W)is used, the optimal width accommodating even to the dovetail 31 thebottom width of which becomes larger than the width of the fifth innermetal plate 16 ₅ by the tolerance occurring can be gained. Therefore,the failure of the digging can be made zero (namely, the digging-workyield can be pushed up to 100%).

In addition, by creating an exclusive gauge, the optimal width (namely,the combination of 1W-5L) may be instantly expressed as color by puttingthis gauge in the fixed position of the dug dovetail 31.

Next, the usage of the expansion anchor 10 according to this embodimentis explained with reference to FIGS. 2-4.

First, two cuts, the sectional shape of which is an arc, are formedusing a diamond wheel saw 21 shown in FIG. 2A in the base material 30(such as a concrete and a stone) by the rotational movement of the wheelin which the diamond chips 22 are provided.

Thereafter, using the diamond wheel saw 21, an auxiliary cut is formedto a predetermined depth so that the shape of the two cuts and theauxiliary cut is like “Z” character as shown in FIG. 3A. Then, as shownin FIG. 3B, the acute-angle portion of the auxiliary cut (the portionapplied black in this drawing) of the “Z” character-like cuts is hitusing the chisel. Then, while the unnecessary base material 30 isremoved, the remaining portion (the portion applied black in thisdrawing) of the “Z” character-like cut is hit using a chisel as shown inFIGS. 3C and 3D. When the remaining base material 30 is not exfoliated,the bottom thereof is swept away using the chisel.

Thereby, the “−” character-like dovetail 31 with the mouth width W1 andthe bottom width W2 (W1<w2) as shown in FIG. 4A is formed in the basematerial 30.

When only the imperfect dovetail is formed in this method, the dovetailis suitably formed using the diamond wheel saw 21, a diamond cutter, adiamond disc sander, or a diamond chain saw. The smoothness of thesurface of the dovetail 31 is unnecessary. Rather, when the unevennessremains, the effect of the adhesive becomes better.

Moreover, when the cutting-slant is not applied, after removing themarking dimensions, the dovetail 31 the bottom width W2 of which islager than the mouth width W1 can be easily formed by repeating theoperation in which the blade edge of the diamond wheel saw 21 is pushedand leaned.

Furthermore, since the anchor design, in which the expansion anchor 10spreads to the internal fixed distance even in the shorten portion ofthe blade, is applied, the anchor effect can be demonstrated in thewhole contact dovetail surface.

Using a chain saw 25 shown in FIG. 2B instead of the diamond wheel saw21, a “−” character-like shaped dovetail 31′ with the mouth width W1 andthe bottom width W2 (W1<W2) shown in FIG. 4B may be formed in the basematerial 30 by the rotational movement of the chain in which diamondchips 26 are provided.

When the dovetail 31 is formed in the base material 30 as mentionedabove, the anchor bolt 11 (refer to FIG. 1) is inserted into thedovetail 31 so that the bolt head turns down. Then, after the anchorbolt 11 is penetrated in the penetration-hole of the fifth inner metalplate 16 ₅, the fifth inner metal plate 16 ₅ is inserted into thedovetail 31 by the fifth inner metal plate 16 ₅ being inclined aslantagainst the mouth surface of the dovetail 31 (namely, making theplane-projection-area small) and is made to pass through the mouth ofthe dovetail 31 utilizing the margin of the penetration-hole. Thereby,even if the fifth inner metal plate 16 ₅ the width 5W of which is largerthan the mouth width W1 of the dovetail 31 is used, it is possible toinsert it into the dovetail 31.

Then, the fourth to first inner metal plates 16 ₄-16 ₁ are inserted intothe dovetail 31. At this time, the fourth to first inner metal plates 16₄-16 ₁ the width of which is larger than the mouth width W1 of thedovetail 31 are inserted by inclining aslant as well as the fifth innermetal plate 16 ₅. The direction of the first to fifth inner metal plates16 ₁-16 ₅ is the same (an anchor-bolt and inner-metal-plate insertionstep).

At this time, when the base material 30 is a floor, the anchor bolt 11and the first to fifth innermetal plates 16 ₁-16 ₅ are dropped into thebottom of the dovetail 31 using attraction.

Moreover, when the base material 30 is a ceiling, any one of the firstto fifth inner metal plates 16 ₁-16 ₅, the width of which is larger thanthe mouth width of the dovetail 31, is caught, so that the insertedanchor bolt 11 and the first to fifth inner metal plates 16 ₁-16 ₅ donot fall. When the drop of the anchor bolt 11 and the first to fifthinner metal plates 16 ₁-16 ₅ is prevented by another method such as bypressing down by a hand, the widths 1W-5W of the first to fifth innermetal plates 16 ₁-16 ₅ may be smaller than the mouth width W1 of thedovetail 31.

Thereafter, while the inserted anchor bolt 11 and first to fifth innermetal plates 16 ₁-16 ₅ are pushed against the bottom of the dovetail 31,the first and second outer plates 15 ₁, 15 ₂ are inserted into thedovetail 31 one by one so that the external surfaces of the first andsecond outer plates 15 ₁, 15 ₂ may touch the side-wall of the dovetail31 certainly and naturally (an outer-plate imposition step).

Since a space of a certain size is generated in the bottom of thedovetail 31 in this step by experience, the smooth imposition operationto the dovetail 31 and the most importantanchor-axis-upright-rectification can be carried out freely.

Moreover, when the side-walls of the dovetail 31 do not face each otherat equal intervals of the longitudinal direction of the dovetail 31, thefollowing measures are taken.

(1) An elastic adhesive, epoxy adhesive, or a cement mortar is pouredbetween the side-wall of the dovetail 31 and the first and second outerplates 15 ₁, 15 ₂ and is stiffened.(2) The position adjustment is carried out by inserting the wedges atone to four places between the first and second outer plates 15 ₁, 15 ₂and the first to fifth inner metal plate 16 ₁-16 ₅ from the right andleft of the longitudinal direction of the dovetail 31, and then they arelocked up eternally. In this case, it is safer to fill up the cavity ofthe dovetail 31 with an adhesive or a cement mortar.

Then, the anchorage metal plate 14 is inserted into the anchor bolt 11by passing the bolt-screw portion of the anchor bolt 11 through thepenetration-hole of the anchorage metal plate 14 (an anchorage mountstep).

Thereby, the anchorage metal plate 14 bridges the side-wall of thedovetail 31 on the surface of the base material 30. Since the anchoragemetal plate 14 planarly contacts with the surface of the base material30 together with the anchorage after being locked up, the short-termload and the long-term load (tensile force and shearing force) aretransformed into the compression force against the base material 30.

Furthermore, the anchorage metal plate 14 is effective in not causingthe partial displacement of the first and second outer plates 15 ₁, 15 ₂when they are locked up as mentioned later.

Finally, the locked-up operation is carried out using the spring washer13 and the nut 12 (a locked-up step).

Thereby, the first to fifth inner metal plates 16 ₁-16 ₅ begin thedisplacement in the mouth direction of the dovetail 31, and the firstand second outer plates 15 ₁, 15 ₂ stick to the side-walls of thedovetail 31 to begin to demonstrate the anchor adhesion. However, it isnot necessary to apply the unnecessary torque, and the shakiness shouldjust be solved.

FIGS. 5A-5D show the states of the locked-up expansion anchor 10.

In the expansion anchor 10 according to this embodiment, it is notnecessary to give the anchor-expansion stress, because the anchor itselfdoes not theoretically need to be fixed to the base material 30 unlikethe conventional circular-hole anchor. That is, since only the value ofthe real number of the generated load serves as the adhesion force andacts to the base material 30, the structure in which any superfluousstress is not given at all is realized. Therefore, the locking-upoperation may be carried out without causing the shakiness to therespective parts and components. Furthermore, in case of the permanentanchoring, it is sufficient to stop the shakiness by filling up thecavity of the base material 30 with silicon coking or a cement mortar.In the established base material concrete, the “concrete stiffenermethod by epoxy resin pouring” which is already announced by theJapanese Concrete Institute may be performed.

In comparison with the hammer-drill boring method (the vibration to thebase material is unescapable) used abundantly in the conventionaltechnology, the dig method using the diamond wheel saw 21 (sandblast)and the expansion anchor 10 according to this embodiment do not give anyunnecessary stress (mechanical vibration and internal expansion force)to the base material 30. Therefore,

(1) In the precast concrete, the strength on the test result table bythe public institution which the maker announced (in the new-buildingcast-in-place concrete, the concrete strength after the care-of-healthperiod progress of the requirement observance, and in the establishedbuilding, the strength by the test method of the Schmidt hammer in thejob site etc.).(2) The material strength of the steel product, the plastic, etc. usedfor the expansion anchor 10(3) Tensile test valueAnchor conditions: Ordinary-structural rolled steel (Suspended SolidsJIS G 3101)1. Dig depth 40 mm2. Anchor outer depth 30 mm3. Anchor outer dimensions 30×60xt=2 Two right and left4. Anchor inner dimensions (46 to 48)×(26 to 30)xt=4.5 4 sheets(a) A concrete (test-specimen dimensions: 150×150×100 mm)non-reinforcing steel

27. 2 kN/bolt (M12) base material crevice break-down (relief break-downto the crevice and the side surface on the basis of the intersection ofthe side surface and the bottom of the dovetail)

(b) Black granite (test-specimen dimensions: 182×152×117 mm)

40.0 KN/bolt (M12) base material crevice break-down (one dovetail wallextension surface crevice break-down on the basis of the intersection ofthe side surface and the bottom of the dovetail)

The architecture of the anchor bolt and the strength calculation can beperformed only for the above value, so that the pulling-out examinationafter the construction of the on-site becomes unnecessary.

That is, the maximum tensile strength of the expansion anchor 10 becomesthe lower value of the base-material bending moment strength and thebolt yield-stress strength. As a result, if the 150 kN-super-highstrength concrete and the 800 mega pascal super-high tension steel whichare put are utilized for the raw material and the composition elementsof the expansion anchor 10, the drasticsuper-high-strength-post-installed anchor will be born.

The more anchor-imbedding depth is deep, the more the safety rate seemsto improve as long as there is the instability in the base-materialcompression intensity such as the neutralization, cracks, etc. ofconcrete. However, it can reason from the base material break-down andthe break fact in the tensile test concerned that since the origin ofthe anchor proof strength is the counter force over the base-materialbending moment in the expansion anchor 10, the warping cone break-downsecondarily generates, but the imbedding depth and the warping conebreak-down can be free from the anchor-proof-strength origin.

On the practical use target, the practical anchor proof strength can beobtained when any deterioration such as the neutralization does notoccurred within the depth limit (namely, within the “wear” limits) tothe reinforcing steel placed under the concrete surface at 3-5 cm, andit is judged in the Schmidt hammer test that there is the sufficientanchor proof strength. That is, the reinforcing-steel investigation isbeforehand performed like the conventional anchor construction using thetechnical drawing and the probe. When the reinforcing steel isencountered, the digging is stopped if the depth of around 35 mm issecured, and the anchor establishment may be performed in this depth.Furthermore, when the depth is surely secured, the reinforcing steel canbe cut off and removed using the diamond saw under the carefulexamination. In this case, it is important to reinforce thebase-material concrete by the epoxy resin being poured in and filled upin the air gap of the dovetail 31 after the anchor being fixed.

According to the above-mentioned non-patent literature 7 (T. Okada et.al., “Design and Construction of Post-Installed Anchor”, JapanConstruction Anchor Association Recommendation Books), there is thedescription of the experience value “there was 30% or more ofreinforcing-steel encounter in case of the boring depth of 50 mm ormore.” The expansion anchor 10 according to this embodiment opens 100%from the accompanying operation and defect caused by thereinforcing-steel encounter.

Next, an expansion anchor according to the second embodiment of thepresent invention is explained.

An expansion anchor 50 according to this embodiment is used as anexpansion anchor having internal threads at two end portions of a “−”character-like shaped dovetail 31, and has, as shown in FIG. 6, thefirst and second anchor bolts 51 ₁, 51 ₂ (hexagonal-head bolts) madefrom steel, the first and second spring washers 53 ₁, 53 ₂ made fromsteel, an anchorage metal plate 54 made from steel, the first and secondouter plates 55 ₁, 55 ₂ from steel or plastic, and upper and lower innermetal plates 56 ₁, 56 ₂ made from steel.

Here, in the both ends on the center line of the longitudinal directionof the anchorage metal plate 54 (the longitudinal direction of thedovetail 31), the first and second penetration-holes the diameter ofwhich is the almost same as the diameter of the first and second anchorbolts 51 ₁, 51 ₂ are formed, respectively.

In the places corresponding to the first and second penetration-holes ofthe anchorage metal plate 54 on the center line of the longitudinaldirection of the upper inner metal plates 56 ₁ (the longitudinaldirection of the dovetail 31), the first and second upper internalthreads 56 a ₁₁, 56 a ₁₂ by which the tap-processing is carried out toscrew with the first and second anchor bolts 51 ₁, 51 ₂ are formed,respectively. Similarly, the places corresponding to the first andsecond penetration-holes of the anchorage metal plate 54 on the centerline of the longitudinal direction of the lower inner metal plates 56 ₂(the longitudinal direction of the dovetail 31), the first and secondlower internal threads 56 a ₂₁, 56 a ₂₂ by which the tap-processing iscarried out to screw with the first and second anchor bolts 51 ₁, 51 ₂are formed, respectively.

In the expansion anchor 50 according to this embodiment, in order tosecure two screw parts on the upper and lower sides or the right andleft sides, the length (the length of the longitudinal direction of thedovetail 31) and height (the length of the depth direction of thedovetail 31) of the upper and lower inner metal plates 56 ₁, 56 ₂ areset larger than the length and height of the first to fifth inner metalplates 16 ₁-16 ₄ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 56 ₁, 56 ₂ isset large, the upper and lower inner metal plates 56 ₁, 56 ₂ cannot beinserted into the dovetail 31 like the fifth inner metal plate 16 ₅mentioned above. Therefore, the width of the upper and lower inner metalplates 56 ₁, 56 ₂ is set smaller than the mouth width W1 of the dovetail31.

In order to secure the width larger than the mouth width W1 of thedovetail 31 after inserting the first and second outer plates 55 ₁, 55 ₂and the upper and lower inner metal plates 56 ₁, 56 ₂ into the dovetail31, the thickness of the first and second outer plates 55 ₁, 55 ₂ is setlarger than the thickness of the first and second outer plates 15 ₁, 15₂ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 56 ₁, 56 ₂ isset large, the sectional shape of the length direction of the lowerinner metal plate 56 ₂ is made into a reverse-trapezoid shape so that itcan be inserted into the dovetail 31 whose sectional shape along thelength direction is a semicircle shape.

Since each of the first and second outer plates 55 ₁, 55 ₂ has “L”character-like cross-sectional shape which consists of a top plateportion and a side plate portion and the height of the first and secondouter plates 55 ₁, 55 ₂ is set larger than the height of the first andsecond outer plates 15 ₁, 15 ₂ shown in FIG. 1, the width of the sideplate portion is set smaller toward the bottom portion from the centerportion to be able to be inserted into the dovetail 31 whose sectionalshape of the length direction is semicircle-like.

The upper portions (or the whole surfaces) of the two side surfaces ofthe upper and lower inner metal plates 56 ₁, 56 ₅ are subjected to thechamfering-processing so that they become the continuation surfaces withthe same inclination angle as the side-wall of the dovetail 31 when theupper inner metal plate 56 ₁ is piled up on the lower inner metal plate56 ₅ in the same direction. Although it is more desirable that the upperand lower inner metal plates 56 ₁, 56 ₅ are subjected thechamfering-processing, they may be ones which are manufactured by beingextracted by the press-working machine and are not subjected thechamfering-processing.

Moreover, the side plate portions of the first and second outer plates55 ₁, 55 ₂ are bent to the top plate portions of the first and secondouter plates 55 ₁, 55 ₂ at the inclination angle so that the side plateportions become parallel to the side-walls of the dovetail 31 wheninserting the first and second outer plates 55 ₁, 55 ₂ into the dovetail31 so that the end surfaces of the top plate portions face each other.That is, the first and second outer plates 55 ₁, 55 ₂ are subjected tothe dovetail-correspondence elevation-angle bending-processing. Althoughit is more desirable that the side plate portions of the first andsecond outer plates 55 ₁, 55 ₂ are subjected to thedovetail-correspondence elevation-angle bending-processing, they may beones which are manufactured by cutting the ready-made article angle (forexample, a right-angled bending material like an iron-material anglecutting plane).

Next, the usage of the expansion anchor 50 according to this embodimentis explained.

First, the dovetail 31 shown in FIG. 4A is formed in the base material30 using the diamond wheel saw 21 shown in FIG. 2A like the case of theexpansion anchor 10 according to the first embodiment mentioned above.

Thereafter, the lower inner metal plate 56 ₂ is dropped into thedovetail 31, and then the upper inner metal plate 56 ₁ is dropped on thelower inner metal plate 56 ₂ (an inner-plate imposition step).

Thereafter, the first and second outer plates 55 ₁, 55 ₂ are insertedinto the dovetail 31 one by one so that the external surfaces of thefirst and second outer plates 55 ₁, 55 ₂ may touch the side-wall of thedovetail 31 certainly and naturally (an outer-plate imposition step).

Thereafter, the anchorage metal plate 54 is placed on the surface of thebase material 30 to cover all the opening portions of the dovetail 31(an anchorage mount step).

Here, in case of using the expansion anchor 50 as objects for fixing ahand-rail etc. which is attached to the wall, a hand-rail-leg-wheel flatplate is used as the anchorage metal plate 54. At this time, thehand-rail-leg-wheel flat plate may be designed to be larger than thedovetail 31 in order to cover the dovetail 31.

Thereafter, the first and second anchor bolts 51 ₁, 52 ₂ are passedthrough the first and second penetration-holes of the anchorage metalplate 54 after being equipped with the first and second spring washers53 ₁, 53 ₂, and then the first and second upper internal threads 56 a₁₁, 56 a ₁₂ of the upper inner metal plate 56 ₁ and the first and secondlower internal threads 56 a ₂₁, 56 a ₂₂ of the lower inner metal plate56 ₂ are fastened by the brake torque being averagely applied to thefirst and second anchor bolts 51 ₁, 51 ₂ by turns, (a locked-up step).

Thereby, the upper inner metal plate 56 ₁ and the lower inner metalplate 56 ₂ begin the displacement in the mouth direction of the dovetail31, and the first and second outer plates 55 ₁, 55 ₂ stick to theside-walls of the dovetail 31 to begin to demonstrate the anchoradhesion. However, it is not necessary to apply the unnecessary torque,and the shakiness should just be solved.

FIGS. 7A-7D show the states of the locked-up expansion anchor 50

Next, an expansion anchor according to the third embodiment of thepresent invention is explained.

An expansion anchor 60 according to this embodiment is used as anexpansion anchor having internal threads at four end portions of a “+”character-like shaped dovetail 32 (refer to FIG. 10A), and has, as shownin FIG. 8, the first to fourth anchor bolts 61 ₁-61 ₄ (hexagonal-headbolts) made from steel, the first to fourth spring washer 63 ₁-63 ₄ madefrom steel, an anchorage metal plate 64 made from steel, the first toeighth outer plates 65 ₁-65 ₈ made from steel or plastic, and upper andlower inner metal plates 66 ₁, 66 ₂ made from steel.

In FIG. 8, only the first and fourth anchor bolts 61 ₁, 61 ₄ among thefirst to fourth anchor bolts 61 ₁-61 ₄ are showed, and only the firstand fourth spring washers 63 ₁, 63 ₄ among the first to fourth springwasher 63 ₁-63 ₄ are showed.

Here, in the both ends on two center lines (length and width) of theanchorage metal plate 64, the first to fourth penetration-holes thediameter of which is the almost same as the diameter of the first tofourth anchor bolts 61 ₁-61 ₄ are formed, respectively.

Moreover, the upper inner metal plate 66 ₁ and the lower inner metalplate 66 ₂ has the shape similar to the shape of the “+” character-likedovetail 32.

That is, the upper inner metal plate 66 ₁ has the plane shape in whichtwo sticks are intersected in the shape of “+” character (hereafter, toa simplification of explanation sake, the projection portions of theupper inner metal plate 66 ₁ are called the first to fourth upperprojection portions.), and the first to fourth upper internal threads 66a ₁′-66 a ₁₄ by which the tap-processing is carried out to screw withthe first to fourth anchor bolts 61 ₁-61 ₄ are formed in the places ofthe first to fourth upper projection portions which correspond to thefirst to fourth penetration-holes of the anchorage metal plate 64.

Similarly, the lower inner metal plate 66 ₂ has the plane shape in whichtwo sticks are intersected in the shape of “+” character (hereafter, toa simplification of explanation sake, the projection portions of thelower inner metal plate 66 ₂ are called the first to fourth lowerprojection portions.), and the first to fourth lower internal threads 66a ₂₁-66 a 2 ₂₄ by which the tap-processing is carried out to screw withthe first to fourth anchor bolts 61 ₁-61 ₄ are formed in the places ofthe first to fourth lower projection portions which correspond to thefirst to fourth penetration-holes of the anchorage metal plate 64.

In the expansion anchor 60 according to this embodiment, in order tosecure four screw parts on the upper and lower sides and the right andleft sides, the length (namely, the length from the tip of the firstupper projection portion to the tip of the third upper projectionportion, and the length from the tip of the second upper projectionportion to the tip of the fourth upper projection portion) and height(namely, the length of the depth direction of the dovetail 32) of theupper and lower inner metal plates 66 ₁, 66 ₂ are set larger than thelength and height of the first to fifth inner metal plates 16 ₁-16 ₄shown in FIG. 1.

Since the height of the upper and lower inner metal plates 66 ₁, 66 ₂ isset large, the upper and lower inner metal plates 66 ₁, 66 ₂ cannot beleaned and inserted into the dovetail 32 like the first to fifth innermetal plate 16 ₁-16 ₅ shown in FIG. 1. Therefore, the width of the firstto fourth upper projection portions of the upper inner metal plate 56 ₁and the first to fourth lower projection portions of the lower innermetal plate 56 ₂ is set smaller than the mouth width of the dovetail 32.

In order to secure the width larger than the mouth width W1 of thedovetail 32 after inserting the first to eighth outer plates 65 ₁-65 ₈and the upper and lower inner metal plates 66 ₁, 66 ₂ into the dovetail32, the thickness of the first to eighth outer plates 65 ₁-65 ₈ is setlarger than the thickness of the first and second outer plates 15 ₁, 15₂ shown in FIG. 1.

Since the height of the upper and lower inner metal plates 66 ₁, 66 ₂ islarge, the tips of the first to fourth projection portions of the lowerinner metal plate 66 ₂ are cut by the acute angle to be inserted intothe dovetail 32 whose sectional shape of the longitudinal direction isthe semicircle shape.

Each of the first to eighth outer plates 65 ₁-65 ₈ has the “L”character-like cross-sectional shape which consists of a top plateportion and a side plate portion, and since the height of the first toeighth outer plates 65 ₁-65 ₈ is set larger than the height of the firstand second outer plates 15 ₁, 15 ₂ shown in FIG. 1, the width of theside plate portions is set smaller toward the bottom portion from thecenter portion to be inserted to near the bottom of the dovetail 32whose sectional shape of the longitudinal direction is the semicircleshape.

Moreover, the upper portions (or the whole surfaces) of the two sidesurfaces of the longitudinal direction of the first to fifth upperprojection portions of the upper inner metal plate 66 ₁ and the first tofifth lower projection portions of the lower inner metal plate 66 ₂ aresubjected to the chamfering-processing so that they become thecontinuation surfaces with the same inclination angle as the side-wallof the dovetail 32 when the upper inner metal plate 66 ₁ is piled up inthe same direction on the lower inner metal plate 66 ₂. However,although it is more desirable that the upper and lower inner metalplates 66 ₁, 66 ₂ are subjected the chamfering-processing, they may beones which are manufactured by being extracted by the press-workingmachine and are not subjected the chamfering-processing.

Moreover, the side plate portions of the first to eighth outer plates 65₁-65 ₈ are bent to the top plate portions of the first to eighth outerplates 65 ₁-65 ₈ at the inclination angle so that the side plateportions become parallel to the side-walls of the dovetail 32 wheninserting the first to eighth outer plates 65 ₁-65 ₈ into the dovetail32 so that the end surfaces of the top plate portions face each other.That is, the first to eighth outer plates 65 ₁-65 ₈ are subjected to thedovetail-correspondence elevation-angle bending-processing. Although itis more desirable that the first to eighth outer plates 65 ₁-65 ₈ aresubjected to the dovetail-correspondence elevation-anglebending-processing, they may be ones which are manufactured by cuttingthe ready-made article angle (for example, a right-angled bendingmaterial like an iron-material angle cutting plane).

Next, the usage of the expansion anchor 60 according to this embodimentis explained with reference to FIGS. 9-11.

First, two cuts whose sectional shape is an arc are formed, using thediamond wheel saw 21 shown in FIG. 2A, in the base material 30 (such asa concrete and a stone) by the rotational movement of the wheel in whichthe diamond chips 22 are provided as shown in FIG. 9A, and then twoother cuts whose sectional shape is an arc are formed in parallel in thebase material 30 to cross right-angled at the center of the two cuts.

Thereafter, as shown in FIG. 9B, the intersection portion of the fourcuts (the portion applied black in this figure) is hit using the chisel.Then, while the unnecessary base material 30 is removed, the remainingportions (the portions applied black in this figure) between the twoparallel cuts are hit using the chisel as shown in FIGS. 9C and 9D. Whenthe remaining base material 30 is not exfoliated, the bottom thereof isswept away using the chisel.

Thereby, the “+” character-like dovetail 32 which has the mouth widthW1, the bottom width W2, the mouth intersection-portion diagonal-linelength W3 and the bottom intersection-portion diagonal-line length W4(W1<W2<W3<W4) as shown in FIG. 10A is formed in the base material 30.

Using the chain saw 25 shown in FIG. 2B, a “+” character-like shapeddovetail 32′ shown in FIG. 10B may be formed in the base material 30similarly.

Thereafter, the lower inner metal plate 66 ₂ is dropped into thedovetail 32, and then the upper inner metal plate 66 ₁ is dropped on thelower inner metal plate 66 ₂ (an inner-plate imposition step).

Thereafter, the first to eighth outer plates 65 ₁-65 ₈ are inserted intothe dovetail 32 one by one so that the external surfaces of the first toeighth outer plates 65 ₁-65 ₈ may touch the side-wall of the dovetail 32certainly and naturally (an outer-plate imposition step).

Thereafter, the anchorage metal plate 64 is placed on the surface of thebase material 30 to cover all the opening portions of the dovetail 32(an anchorage mount step).

Here, in case of using the expansion anchor 60 as objects for fixing inthe leg portion of the angle stiff pipe pillar, the round stiff-pipepillar, etc., the flat-bar sheet steel which is attached in the legportion of the pillar by welding and so forth and in which four holesare formed is used as the anchorage metal plate 64.

Thereafter, the first to fourth anchor bolts 61 ₁-62 ₄ are passedthrough the first to fourth penetration-holes of the anchorage metalplate 64 after being equipped with the first to fourth spring washers 63₁-63 ₄, and then the first to fourth upper internal threads 66 a ₁₁-66 a₁₂ of the upper inner metal plate 66 ₁ and the first to fourth lowerinternal threads 66 a ₂₁-66 a ₂₂ of the lower inner metal plate 66 ₂ arefastened by the brake torque being averagely applied to the first tofourth anchor bolts 61 ₁-61 ₂ by turns, (a locked-up step).

Thereby, the upper inner metal plate 66 ₁ and the lower inner metalplate 66 ₂ begin the displacement in the mouth direction of the dovetail32, and the first to eighth outer plates 65 ₁-65 ₈ stick to theside-walls of the dovetail 32 to begin to demonstrate the anchoradhesion. However, it is not necessary to apply the unnecessary torque,and the shakiness should just be solved.

FIGS. 11A-11D show the states of the locked-up expansion anchor 60

In the above explanation, although the anchorage metal plates 14, 54, 64made from steel are used, the roves made from steel may be used.

1. An expansion anchor for use in combination with a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising: an anchor bolt; two or more inner metal plates inserted into said dovetail; and two outer plates inserted between two side-walls of said dovetail and said inner metal plates, wherein each of said two outer plates has a substantially L-shaped cross-section which comprises a top plate portion and a side plate portion.
 2. An elongated expansion anchor having a threaded portion in a center portion thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising: an anchor bolt; a nut; first and second outer plates; and two or more inner metal plates, wherein each of said first and second outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; and wherein a width of a first inner metal plate is selected to be greater than a width of a second inner metal plate.
 3. The expansion anchor according to claim 2, wherein a length of said second inner metal plate is selected to be greater than the width of said first inner metal plate, so that side surfaces of said first and second inner metal plates become surfaces having the same inclination angle as a side-wall of said dovetail when said first inner metal plate is turned 90 degrees to be stacked with said second inner metal plate.
 4. The expansion anchor according to claim 2, wherein a width of at least one inner metal plate of said two or more inner metal plates is selected to be larger than the mouth width of said dovetail; and wherein a penetration-hole, a bore of which is larger than a diameter of said anchor bolt, is provided in a center portion of at least one inner metal plate of said two or more inner metal plates.
 5. An elongated expansion anchor having threaded portions in opposed end portions thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, the expansion anchor comprising: first and second anchor bolts; first and second outer plates; and an upper inner metal plate and a lower inner metal plate, wherein each of said first and second outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; and wherein each of said upper inner and lower inner metal plates includes first and second upper internal threaded portions formed in respective holes defined therein, to enable threaded engagement with said first and second anchor bolts.
 6. The expansion anchor according to claim 5, wherein a width of each of said upper and lower inner metal plates is selected to be smaller than the mouth width of said dovetail; a cross-sectional shape of said lower inner metal plate viewed from a side thereof is substantially trapezoidal; and a width of said side plate portions of said first and second outer plates is selected to be less in a bottom portion thereof than in a central portion thereof.
 7. A substantially cross-shaped expansion anchor having internal threaded portions defined in four end portions thereof, the expansion anchor being configured to engage a dovetail, a mouth width of said dovetail being narrower than a bottom width of said dovetail, comprising: first to fourth anchor bolts; first to eighth outer plates; and an upper inner metal plate and a lower inner metal plate, each including first through fourth projection portions, wherein: each of said first to eighth outer plates has a substantially L-shaped cross-section, which comprises a top plate portion and a side plate portion; said upper inner metal plate and said lower inner metal plate have a shape similar to the shape of said dovetail when viewed from a the same direction; and said first to fourth projection portions of each of the upper and lower internal plates respectively include threaded portions formed in respective holes defined therein, to enable threaded engagement with respective ones of said first to fourth anchor bolts.
 8. The expansion anchor according to claim 7, wherein a width of each of said first to fourth upper projection portions of said upper inner metal plate and said first to fourth lower projection portions of said lower inner metal plate is selected to be smaller than the mouth width of said dovetail; tip portions of said first to fourth lower projection portions of said lower inner metal plate are cut by an acute angle toward a bottom portion of said lower inner metal plate; and a width of each of said side plate portions of said first to eighth outer plates is selected to be less in a bottom portion there of than in a central portion thereof.
 9. The expansion anchor according to claim 3, wherein a width of at least one inner metal plate of said two or more inner metal plates is selected to be greater than the mouth width of said dovetail; and a penetration-hole, a bore of which is larger than a diameter of said anchor bolt, is defined in a center portion of said at least one inner metal plate of said two or more inner metal plates. 